Timetable of the Precambrian
4594 Ma: A supernova explosion seeds our galactic neighborhood with heavy elements that will be incorporated into the Earth, and results in a shockwave in a dense region of the Milky Way galaxy. The Ca-Al-rich inclusions, which formed 2 million years before the chondrules, are a key signature of a supernova explosion. **4592.1 Ma: Rapid collapse of hydrogen molecular cloud, forming a third generation Population I star, the Sun. **4592 Ma: A protoplanetary disc (from which the Earth eventually forms) emerges around the young sun, which is in its T Tauri stage. *4567.17 Ma: Earth forms. Hadean eon, Azoic supra-era, and Cryptic era start. **4533 Ma: The Moon forms, probably as a result of a glancing collision with Theia, a protoplanet forming at Earth's L4 or L5 Lagrangian point: see giant impact hypothesis. Earth was covered by a magma ocean 200 kilometres deep resulting from the impact energy from this and other planetesimals during the early bombardment phase, and energy released by the planetary core forming. Outgassing from crustal rocks gives Earth a reducing atmosphere of methane, nitrogen, hydrogen, ammonia, and water vapour, with minor amounts of hydrogen sulfide, carbon monoxide, and carbon dioxide, in that order. With further full outgassing over 1000°-1500°K, nitrogen and ammonia become minor constituents, and comparable amounts of methane, carbon monoxide, carbon dioxide, water vapour, and hydrogen are released. **4450 Ma: 100 million years after the Moon formed, the first lunar crust, formed of lunar anorthosite, differentiates from lower magmas. The earliest Earth crust probably forms similarly out of similar material. On Earth the pluvial period starts, in which the Earth's crust cools enough to let oceans form by accumulating rainwater. **4404 Ma: First known mineral, found at Jack Hills in Western Australia. Detrital zircons show presence of a solid crust and liquid water. Latest possible date for a secondary atmosphere to form, produced by the Earth's crust outgassing, reinforced by water and possibly organic molecules delivered by comet impacts and Carbonaceous Chondrites (including type CI shown to be high in a number of amino acids and polycyclic aromatic hydrocarbons (PAH)). *4150 Ma: Basin Groups unofficial period starts. **4100 Ma: Acasta Gneiss of Canada, first known rock. *3920 Ma: Nectarian unofficial period starts. **3900 Ma: Late heavy bombardment of the Moon (and probably of the Earth as well) by asteroids. *3850 Ma: Lower Imbrian unofficial period starts. **3850 Ma: First evidence of life: Akilia island graphite off Western Greenland contains evidence of kerogen, of a type consistent with photosynthesis. Azoic supra-era ends. *3800 Ma: Archean eon and Eoarchean era start. *3600 Ma: Paleoarchean era starts. **3460 Ma: Fossils of bacteria in chert. *3200 Ma: Mesoarchean era starts. *2800 Ma: Neoarchean era starts. *2500 Ma: Proterozoic eon, Paleoproterozoic era, and Siderian period start. Banded iron formations form during this period. Earth's atmosphere starts to become oxygenic. **2400 Ma: Huronian glaciation starts. *2300 Ma: Rhyacian period starts. **2100 Ma: Huronian glaciation ends. *2050 Ma: Orosirian period starts. Significant orogeny in most continents. **2023 Ma: Vredefort impact structure forms. **2000 Ma: The minor supercontinent Atlantica forms. **1850 Ma: Sudbury impact structure. Penokean orogeny. *1800 Ma: Statherian period starts. **1800 Ma: Supercontinent Columbia forms, one of whose fragments being Nena. *1600 Ma: Mesoproterozoic era and Calymmian period start. Platform covers expand. **1500 Ma: Supercontinent Columbia breaks up *1400 Ma: Ectasian period starts. Platform covers expand. **1300 Ma: Grenville orogeny starts. **1200 Ma: Red alga Bangiomorpha pubescens, first known sexually reproducing organism. *1200 Ma: Stenian period starts, during which supercontinent Rodinia comes together. **1000 Ma: Grenville orogeny ends. *1000 Ma: Neoproterozoic era and Tonian period starts. First radiation of acritarchs. Rodinia starts to break up. **1000 Ma: Animal tracks in India and Australia. *850 Ma: Cryogenian period starts, during which Earth entirely freezes over (Snowball Earth) at least 3 times. **750 Ma: Sturtian glaciation starts. Rodinia splits. **700 Ma: Worm impressions in China. **685 Ma: Varanger glaciation begins. **635 Ma: Varanger glaciation ends. *635 Ma: Ediacaran period begins. **600 Ma: Pan-African orogeny. Supercontinent Pannotia forms. **575 Ma: First Ediacaran-type fossils. **560 Ma: Trace fossils, e.g., worm burrows, and small bilaterally symmetrical animals. **540 Ma: Pannotia breaks up. **544 Ma: The small shelly fauna first appears. *542 Ma: Phanerozoic eon, Palaeozoic era, and Cambrian period begin. Etymology of Proterozoic geological period names See also * Precambrian * Geologic time scale Category:Geochronology Category:Precambrian Category:Earth sciences Category:Geology Category:Geology timelines